[PATCH] D124982: [clang][OpenMP][DebugInfo] Debug support for variables in containing scope of OMP constructs

[Alok Kumar Sharma via Phabricator via cfe-commits]

alok created this revision.
alok added reviewers: aprantl, djtodoro, jmorse, jini.susan.
alok added a project: debug-info.
Herald added subscribers: guansong, hiraditya, yaxunl.
Herald added a project: All.
alok requested review of this revision.
Herald added a reviewer: jdoerfert.
Herald added subscribers: llvm-commits, cfe-commits, sstefan1.
Herald added projects: clang, LLVM.

In case of OpenMP, compilers generate encapsulates code present in
OpenMP construct to artificial functions. This is done to apply parallelism
to block of code. In context of these blocks, currently containing scope
variables are not accessible. This is due to new artificial function DIE being
in global scope.
As from user point of view, containing scope is same lexical scope, there
must be correct DIE hierarchy for artificial functions, which should be child
of containing scope.
Please consider below testcase.

   1  #include <stdio.h>
   2  #include <stdlib.h>
   3
   4  int global_var1;
   5  int global_var2 = 99;
   6  int foo(int n) {
   7    int same_var = 5;
   8    int other_var = 21;
   9    int share = 9, priv, i;
  10    global_var1 = 99;
  11
  12    if (n < 2)
  13      return n;
  14    else {
  15      int same_var = rand() % 5;
  16      int local_var = 31;
  17  #pragma omp parallel for
  18      for (i = 0; i < n; i++) {
  19        share += i;  // <-------------- (A)
  20      }
  21      return share;
  22    }
  23  }
  24
  25  int main() {
  26    int n = 10;
  27    printf("foo(%d) = %d\n", n, foo(n));
  28    return 0;
  29  }

Please consider the line# 19, user expects variables "same_var", "local_var", "other_var" to be
accessible inside debugger but which is not possible.

  (gdb) p same_var
  No symbol "same_var" in current context.
  (gdb) p other_var
  No symbol "other_var" in current context.
  (gdb) p local_var
  No symbol "local_var" in current context.

After current patch.

  (gdb) thr 1
  [Switching to thread 1 (Thread 0x7ffff7c1c400 (LWP 17992))]
  #0  .omp_outlined._debug__ (.global_tid.=0x7fffffffdad0, .bound_tid.=0x7fffffffdac8, n=@0x7fffffffdf18: 10, share=@0x7fffffffdf0c: 9) at 1.c:19
  19            share += i;
  (gdb) p same_var
  $1 = 3
  (gdb) p local_var
  $2 = 31
  (gdb) p other_var
  $3 = 21


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124982

Files:
  clang/lib/CodeGen/CGDebugInfo.cpp
  clang/lib/CodeGen/CGDebugInfo.h
  clang/lib/CodeGen/CGOpenMPRuntime.cpp
  clang/lib/CodeGen/CGOpenMPRuntime.h
  clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
  clang/lib/CodeGen/CGOpenMPRuntimeGPU.h
  clang/lib/CodeGen/CGStmtOpenMP.cpp
  clang/lib/CodeGen/CodeGenFunction.cpp
  clang/test/OpenMP/debug_containing_scope.c
  llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
  llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
  llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D124982.427199.patch
Type: text/x-patch
Size: 39376 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20220505/92cac8c5/attachment-0001.bin>